Mammograms are generally obtained by pressing the breast between two plates of imaging radiation transparent material, and taking an image of the compressed breast tissue. The image may be X-ray or another type of image. In theory, the two plates should be parallel to take a perfect quality picture. However, in reality, the pectoral muscle and tissue inhomogeneity affect the shape of the compressed breast, by keeping the two plates from being parallel.
FIG. 1A illustrates one example of the breast tissue 110 compressed between the film cassette 120 and compression plate 130 from the cranial caudal view. As can be seen, the two plates 120, 130 are not parallel. This results in a lighter 140 and darker 145 region of the image.
Similarly, FIG. 1B illustrates the mediolateral oblique view of the compressed breast, showing that the pectoral muscle attachments 160, 170 cause the two plates 120, 130 to not be parallel. Because the image derived is a two-dimensional image, the increased thickness of the breast tissue results in a gray-scale differential between the areas of the breast.
Such a change in the relative color of the image reduces the accuracy of abnormality detection. Therefore, a system that corrects for the tilt, without requiring alteration of the existing structures would be advantageous.